Influência do estádio fenológico da soja e da profundidade de coleta do solo e raiz sobre a densidade populacional de Helicotylenchus dihystera

Abstract

Soybean crop is considered the most important leguminous crop in the world. Besides being the largest producer of the grain, Brazil is also ahead as the largest exporter. However, in order to achieve a large production soybean farmers across the country face some phytosanitary problems and among them the plant-parasitic nematodes. The nematode Helicotylenchus dihystera (known as “spiral nematode”) has shown an increasing population growth rate, causing concern to soybean producers. For an effective control of this pathogen It is essential to identify and estimate the population in the field and for that It is necessary to perform a correct sampling. Authors often have differing opinions about the procedures that need to be followed in this process. With that in mind, the objective of this work was to determine the best stage of soybean development and the depth to perform soil and root sampling in which the H. dihystera population has the highest population level. The experiment was carried out during the 2019/2020 season at the Muller Farm, located in Nova Xavantina, Mato Grosso state, Brazil, the sampling were carried out at 3 different points within the perimeter during the R1, R3, R5.1, R5.3 and R6 stages and were taken at depths of 0-10 cm, 10-20 cm and 20-30 cm. For the extraction of nematodes from soil samples flotation and centrifugation method in sugar solution was used as described by Jenkins (1964). For the samples extraction of roots, the method described by Coolen & D'Herde (1972). The depth of sampling was the only factor that significantly influenced all the variables analyzed (mass of root, population of H. dihystera in the roots and population of H. dihystera in the soil), regardless of the stage of soybean development in which they were carried out. Thus, it is concluded that the soil and soybean roots sampling to achieve the highest population level of H. dihystera must be performed at a depth of 0 to 10 cm, regardless of the reproductive stage.